8p.cT.XX.il. OF VERTIGO. 279 



as jufl before we fall aileep, or between our reve- 

 ries when awake, thefe irritative ideas of motion 

 and found are mod liable to be perceived ; as thofe 

 who have been at fea, or have travelled long in a 

 coach, feem to perceive the vibrations of the (hip, 

 or the rattling of the wheels, at thefe intervals ; 

 which ceafe again, as foon as they exert their atten- 

 tion. That is, at thofe intervals they attend to the 

 apparent motions, and to the battement of founds 

 of the bodies around them, and for a moment 

 miftake them for thofe real motions of the (hip, 

 and noife of wheels, which they had lately been 

 accuftomed to : or at thefe intervals of reverie, or 

 on the approach of fleep, thefe fuppofed motions 

 or founds may be produced entirely by imagina- 

 tion. 



We may conclude from this account of vertigo, 

 that fea-ficknefs is not an effort of nature to relieve 

 herfelf,, but a neceffary confequence of the affocia- 

 tions of catenations of animal motions. And may 

 thence infer, that the vomiting, which attends the 

 gravel in the ureter, inflammations of the bowels, 

 and the commencement of fome fevers, has a fimi- 

 lar origin, and is not always an effort of the vis 

 medicatrix naturae. But where the adion of the 

 organ is the immediate confequence of the (limu- 

 lating caufe, it is frequently exerted to dillodge 

 that iiimulus, as in vomiting up an emetic drug ; 

 at other times, the aftion of an organ is a general 

 effort to relieve pain, as in convulsions of the loco- 

 motive mufeles ; other actions drink up and carry 

 on the fluids, as in abforption and fecretion ; all 

 which may be termed efforts of nature to relieve, 

 or to preferve herfelf. 



u. The cure of vertigo will frequently depend 

 on our previoufly inveftigating the caufe of it, which 

 irom what has been delivered above may originate 

 from the diforder of any part of the great trihes of 



irritative 



